1. Field of the Invention
This invention relates to catalysis. In one aspect, the invention relates to the catalytic oxydehydrogenation of saturated, lower aliphatic acids and esters to the corresponding unsaturated acids and esters while in another aspect, the invention relates to the manufacture of methacrylic acid by the oxydehydrogenation of isobutyric acid with a heteropolyacid, tellurium-containing catalyst.
2. Description of the Prior Art
U.S. Pat. No. 4,061,673 teaches the manufacture of methacrylic acid by the oxidative dehydrogenation of isobutyric acid using a heteropolyacid consisting of molybdenum, tungsten, vanadium, phosphorus and oxygen. The catalyst is supported on a carrier having a silicon dioxide content of at least 70% and a water absorbability of at least 60%.
U.S. Pat. No. 3,917,673 teaches the synthesis of unsaturated, lower aliphatic acids and esters by the catalytic oxidative dehydrogenation of the corresponding saturated acids and esters. The catalyst is the calcined residue of a mixture of bismuth oxynitrate, iron phosphate and lead phosphate.
Other processes and catalysts are known for the oxidative dehydrogenation of isobutyric acid and similar materials to methacrylic acid and similar products. Representative of these include DT No. 2,438,464, BE No. 848,300 and Japanese patent applications Nos. 3,082,720, 2,105,112, 2,105,113, 1,118,718, 2,039,622 and 2,031,018.
Heteropolyacid, tellurium-containing catalysts are known to be useful for the manufacture of methacrylic acid from methacrolein. See for example JAP application No. 2,051,316, GB No. 1,478,828 and NL No. 7602-438.